Afterburner

ABSTRACT

An afterburner to be associated with an incinerator or furnace, or other processing equipment for providing complete combustion of the combustible materials in the exhaust gases or process fumes and vapors. The afterburner comprises an outer closed refractory casing, and an inner cylindrical refractory member is spaced inwardly from the outer casing to provide an outer annular chamber therebetween. The upper end of the inner member is spaced from the top of the casing to provide an upper chamber that establishes communication between the outer annular chamber and the interior of the inner member. The exhaust gases from the incinerator or furnace are introduced tangentially into the lower end of the outer chamber and pass upwardly with a swirling motion to the upper chamber and then downwardly into the interior of the inner member. The gases are discharged from the inner member through a vertical stack assembly which is located centrally of the inner member. Fuel and air are introduced into the lower end of the outer chamber along with the exhaust gases and ignited to burn the combustible products in the gases. To provide complete combustion of the combustible products, the stack assembly includes an outer stack which is spaced outwardly from the inner stack to provide an air passage therebetween. Air passing within the passage is heated and merges with the exhaust gases to provide a secondary stage of combustion for the combustible products.

United States Patent Evans et a1.

[15] 3,658,482 [4 1 Apr. 25, 1972 [54] AFTERBURNER [72] Inventors: Marvin Evans, Bayside; David H. Miller,

Whitefish Bay, both of Wis.

[73] Assignee: College Research Corp., Milwaukee, Wis. [22] Filed: Sept. 8, 1970 [21] Appl. No.: 70,015

[52] US. Cl. ..23/277 C, 23/2 C, 23/284,

110/18 A, 110/8 A, 110/] M, 431/5, 431/8, 431/9, 431/173, 431/80 Primary Examiner-James H. Tayman, Jr. An0rneyAndrus, Sceales, Starke & Sawall [511 1 ABSTRACT An afterbumer to be associated with an incinerator or furnace, or other processing equipment for providing complete combustion of the combustible materials in the exhaust gases or process fumes and vapors. The afterburner comprises an outer closed refractory casing, and an inner cylindrical refractory member is spaced inwardly from the outer casing to provide an outer annular chamber therebetween. The upper end of the inner member is spaced from the top of the casing to provide an upper chamber that establishes communication between the outer annular chamber and the interior of the inner member. The exhaust gases from the incinerator or furnace are introduced tangentially into the lower end of the outer chamber and pass upwardly with a swirling motion to the upper chamber and then downwardly into the interior of the inner member. The gases are discharged from the inner member through a vertical stack assembly which is located centrally of the inner member. Fuel and air are introduced into the lower end of the outer chamber along with the exhaust gases and ignited to burn the combustible products in the gases. To provide complete combustion of the combustible products, the stack assembly includes an outer stack which is spaced outwardly from the inner stack to provide an air passage therebetween. Air passing within the passage is heated and merges with the exhaust gases to provide a secondary stage of combustion for the combustible products.

14 Claims, 2 Drawing Figures Patented April 25, 1972 3,658,482

FIG l A f f ,0 J

\ l" INVENTOR. j DAVID HMlLLER FIG 2 a x MARVIN EVANS "l4; iz/zgm Attor n zys AFTERBURNER This invention relates to an afterburner to be associated with an incinerator or furnace to provide complete combustion of the combustible products in the exhaust gases discharged from the incinerator or furnace.

Atmospheric pollution is caused, at least in part,. by the discharge of odors, and exhaust gases from incinerators, furnaces, and other burning units. These exhaust materials, resulting from incomplete combustion cause obnoxious odors, can be hazardous to the health and can have an adverse effect on the growth of plant life. Because of the increased degree of atmospheric pollution, there has been increased activity in the development of devices to be associated with incinerators or furnaces to provide complete combustion of the combustible waste products in the exhaust gases.

The present invention is directed to an afterburner to be associated with an incinerator or furnace which will provide complete combustion of the waste products in the exhaust gases. The afterburner of the invention includes an outer closed refractory casing and an inner cylindrical refractory member is spaced inwardly of the casing to provide an outer annular chamber therebetween, while the interior of the inner member defines an inner chamber. The upper end of the inner member is spaced from the top of the casing to define an upper chamber that establishes communication between the outer and inner chambers.

The exhaust gases from an incinerator or furnace are introduced under pressure through a tangential inlet into the lower end of the outer chamber. In addition, fuel and air are supplied adjacent to the exhaust gas inlet and ignited to burn the combustible waste products in the exhaust gas. Due to the tangential inlet, the gases swirl upwardly 'within the outer chamber and downwardly within the inner chamber, and are discharged through an inner stack which is located centrally of the inner chamber.

To provide complete combustion of the combustible I products, an outer stack is spaced radially outward from the upper end of the inner stack to provide an air passage between the stacks. The lower end of the passage is open and the upper end of the outer stack terminates above the upper end of the inner stack with the result that air passes through the passage, and heated air merges with the gases at the end of the inner stack to provide a secondary combustion zone to provide complete combustion of the combustible products in the gas.

Additional air can be selectively supplied to both the outer chamber and the inner chamber to aid in the combustion and decrease the stack temperature.

The heavy refractory construction of the outer casing and inner member provides storage of heat for controlled sustained combustion. Due to the swirling flow of the gases within the unit, heavier particles in the combustion gases are thrown outwardly by centrifugal force against the hot refractory walls and this action holds the particles against the heated surfaces for a longer period of time to provide more effective combustion of the heavier particles.

Each succeeding chamber within the afterburner has a larger volume, meaning that the inner chamber has a larger volume than the upper chamber, which in turn has a larger volume than the outer or inlet chamber. This progressive increase in volume reduces the velocity of the combustible waste particles in the exhaust gas so the heavier particles tend to settle out within the inner chamber.

The afterburner also includes a temperature control system in which a thermocouple is mounted within the combustion chamber and is operably connected to a valve in the gas supply line to the burner so that the gas supply is regulated by the temperature in the combustion chamber, thereby providing a more uniformly controlled combustion process.

As the system is pressurized, a high stack is not required to provide a draft, so the afterburner can be used in locations where it would not be feasible to utilize a high stack.

Other objects and advantages will appear in the course of the following description.

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is vertical section of the afterburner of the invention; and

FIG. 2 is the section taken along line 2-2 of FIG. 1.

The drawings illustrate an afterburner which is adapted to receive the incompletely combusted exhaust gases discharged from a furnace or incinerator and is designed to provide complete combustion of the combustible products in the exhaust gases. The afterburner includes a metal casing 1 form ed of a lower section 2 and an upper section 3. The lower section 2 is supported by a series of legs 4 from the ground or foundation. The abutting edges of the casing sections 2 and 3 are provided with outwardly extending flanges which are connected together by a series of bolts 5.

The casing 1 is lined with a high-temperature refractory material 6 commonly used in furnaces or incinerators and which is capable of withstanding the temperatures developed. Spaced inwardly of the refractory lining 6, is an inner cylindrical member 7 also formed of refractory material. The space between the refractory lining 6 of the casing and the cylindrical member 7 defines an outer annular chamber 8 while the interior of the inner member 7 defines an inner chamber 9. As best illustrated in FIG. 1, the upper end of the cylindrical member 7 terminates short of the upper end of the casing 1 to provide an upper chamber 10 that establishes communication between the outer chamber 8 and the inner chamber 9.

As shown in FIG. 2, the casing 1 is provided with an enlarged section 11 which defines a tangential inlet 12 for the introduction of the incompletely combusted exhaust gases from a furnace or incinerator. The inner end of a conduit 13 is connected to the casing 1 in alignment with the inlet 12, while the outer end of the conduit 13 is connected to the outlet 14 of the blower 15. The incompletely combusted exhaust gases from the furnace, incinerator or other combustion device, are drawn to the blower through the inlet 16 and are discharged through the outlet 14 into the inlet 12 of the casing I.

A flap valve 17 is mounted for pivotal movement within the conduit 13 and serves as check valve to permit gas to pass into the casing l but prevents flow of gas in the opposite direction when the unit is idling and the blower 15 is not operating.

As illustrated in FIG. 2, the inlet 12 for the exhaust gases is located tangentially with respect to the outer chamber 8 and this results in the gases moving in a swirling or spiral pattern upwardly within the outer chamber 8.

To burn the combustible waste products in the gas being introduced through inlet 12, a burner unit 18 is located within the enlarged section 11 of the casing and communicates through passage 19 with the lower end of the outer chamber 8. Fuel, such as natural or manufactured gas, oil, or other organic fuel, is supplied to the burner unit 18 through the gas line 20, and a manually operated valve 21 is disposed in the gas line 20 to control the flow of gas within the line. In addition to the manually operated valve 21, an automatic valve 22 is located in gas line 20 and the operation of this valve will be described hereinafter.

Air is supplied to the burner unit 18 through an air line 23 which is connected to the discharge end of a blower 24. A manually operated valve 25 is located in the air line 23 for the .purpose of opening and closing the line.

As shown in FIG. 2, the passage 19 is located tangentially of the chamber 8 and intersects the tangential inlet 12, so that both the exhaust gases from the furnace or incinerator and the fuel-air mixture are provided with a spiral path of flow. The mixture of air and gas in the burner is ignited by a standard igniter device 26 and the flame projects beyond the passage 19 and intersects the passage 12 in the flowpath of the exhaust gas being discharged into the outer chamber 8.

To aid in providing a more efficient combustion additional air can be introduced into the combustion chamber. In this regard, a vertical line 27 is connected to the line 23 and the vertical line is connected to a pair of horizontal lines 28 and 29.

Line 28 is connected to a tangential extending inlet 30 which extends through the wall of the casing and is located approximately at the midpoint of the height of the casing. The upper horizontal line 29 is connected to a downwardly extending inlet 31 which serves to introduce air into chamber 10. Valves 32 and 33 are located within the lines 28 and 29 respectively and serve to control the flow of air therein.

The lower end of the refractory lining 6 is provided with an upstanding projection 34 and the lower end of the cylindrical member 7 is positioned around the projection 34. The upper end of the projection 34 is provided with a generally conical recess 35, and the lower end of the recess is connected to an outlet tube 36 which extends through the lower end of the casing to the exterior. The outlet tube 36 provides an inlet for atmospheric air to be drawn into the inner chamber 9.

The flow of air inwardly through the tube 36 is controlled by an adjustable damper 37. One end of the damper is provided with a pair of lugs 38 which are pivotally connected to a bracket 39 on the lower end of the tube. A rod 40 having its upper end connected to brackets 41 extends through an opening in the damper and a nut is threaded on the end of the rod. By threading the nut up or down on the rod 40 the damper 37 can be pivoted with respect to the tube 36 to thereby control the entry of air inwardly through the tube 36.

The gases pass upwardly within the outer chamber 8 in a swirling or spiral pattern then pass downwardly within the inner chamber 9 in a similar spiral pattern. The gases are withdrawn from the inner chamber 9 through a vertical stack 42 which is located centrally of the inner chamber. The upper end of the stack 42 extends through an opening in the casing l and the stack is welded to a plate 43 which in turn is welded to the outer surface of the casing. To provide a secondary combustion zone and insure complete combustion of the combustible materials in the gases, a second stack 44 is positioned outwardly in spaced relation to the inner stack 42 to provide an annular air passage 45. The lower end of the outer stack 44 is open to the atmosphere and the stack is supported from the plate 43 by a series of legs 46. The outer stack 44 extends through an opening in the roof 47, while the inner stack 42 terminates a substantial distance beneath the upper end of the outer stack;

Air is drawn inwardly through the lower end of the outer stack 44 into passage 45 and is heated as it passes within the passage. The heated air passing upwardly within the annular passage 45 merges with the exhaust gases at the upper end of the inner stack to thereby provide a secondary combustion zone which results in the complete combustion of any remaining combustible material in the exhaust gas.

To provide temperature control for the afterburner, a thermocouple 48 extends through the wall of the casing and is responsive to the temperature within the outer chamber 8. The thermocouple is operably connected to the gas valve 22. The valve 22 is not an on-off type, but instead provides either a high or low gas flow. When the temperature within the outer chamber 8 falls beneath the predetermined setting, the valve 22 is moved to the high position and conversely when the temperature reaches the predetermined setting the thermocouple operates to move the valve 22 to the low flow position. With this system, gas is continuously supplied and ignited within the combustion chamber regardless of whether exhaust gas is introduced into the unit through inlet 12 from the incinerator or furnace. If no waste gases are introduced to the unit, the combustion of the fuel in the burner unit 18 will tend to maintain the afterburner in a heated condition so that it will operate at optimum efficiency when the waste gases are introduced into the unit.

Assuming exhaust gases containing combustible waste products are introduced by blower 15 through inlet 12, the combustible products are combusted by the flame from the burner unit 18 and the gases swirl upwardly within the outer chamber 8. Additional air added through the inlets 30 and 31 aids in providing complete combustion of the combustible products. The gases then pass through the upper chamber l and swirl downwardly within the inner chamber 9 where they are discharged through the stack 42. The swirling action which occurs in both the inner and outer chambers tends to throw the heavier particles of the combustible waste products outwardly against the hot refactory walls and thereby tends to retain the particles in contact with the heated walls for a longer period of time to provide a more effective combustion of the heavier particles.

Chambers 8, 10 and 9 are progressively larger in volume, with the result that the pressure and velocity of the gas will progressively decrease. More specifically, the outer chamber 8 has a lesser volume than the upper chamber 10 which in turn has a lesser volume than the inner chamber 9. This results in the pressure and the velocity of the gas decreasing as the gas moves from the outer chamber through the upper chamber to the inner chamber. The gas within the inner chamber is substantially at atmospheric pressure so that non-pressurized air can be drawn inwardly through the inlet 36 at the bottom of the casing. The decrease in velocity of the gas in the inner chamber is important in that any heavy non-combustible particles will tend to fall by gravity toward the bottom of the inner chamber and will pass along the bottom surface 35 and through the tube 36 to the exterior. The casing can also be provided with an access door, not shown, which provides access to the inner chamber for the purpose of periodically cleaning ash or other products of combustion from the inner chamber.

As previously noted, the stack construction utilizing the inner and outer stacks provides a secondary combustion zone which insures complete combustion of any combustible products in the gases being discharged through the stack. The introduction of air through the tube 36 as well as through the passage 45 between the inner and outer stacks results in a lower stack temperature which provides a longer life for the stack.

The design of the combustion chamber in which the gas moves upwardly through the outer chamber and then downwardly through the inner chamber provides a more effective combustion because it increases the length of travel of the gases through the unit. Moreover, the passages through which the gas travels are relatively narrow so that the combustible products will impinge against the hot refractory walls to increase the effectiveness of the combustion process.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. A combustion device for burning combustible products in a gas, comprising a closed casing including a side wall, a top wall, and a bottom wall, an inner tubular member spaced inwardly of the outer wall of the casing to define an outer chamber therebetween and the interior of said tubular member defining an inner chamber, the lower end of said tubular member being sealed to said lower wall of the casing and the upper end of the tubular member being spaced from the upper wall of the casing to provide a passage that establishes communication between the outer and inner chambers, stack means located within the inner chamber and extending to the exterior of the casing for discharging the gases from the inner chamber, gas inlet means located at the lower end of the outer chamber and extending generally tangentially of said outer chamber for supplying a gas containing combustible products to the outer chamber, said gas passing upwardly in a spiral path in the upper chamber and through said passage and then downwardly in a spiral path through the inner chamber to the lower end of said stack means, and burner means located at the lower end of the outer chamber for burning the combustible products in the gas being introduced through said gas inlet means.

2. The apparatus of claim 1, wherein said casing and said tubular member are formed of refactory material.

3. The apparatus of claim 1, wherein said burner means includes means for introducing fuel to said burner means, blower means for introducing air to said burner means, and ignition means for igniting the fuel and air mixture.

4. The apparatus of claim 3, wherein said means for introducing fuel includes a conduit and valve means located in the conduit, said apparatus also including temperature responsive means responsive to the temperature within the casing and operably connected to said valve means to thereby control the flow of fuel to the burner means in accordance with temperature conditions in said casing.

5. The apparatus of claim 4, wherein said valve means is provided with a high-flow position and a low-flow position and said temperature responsive means operates to move said valve means between said high-flow and low-flow positions.

6. The apparatus of claim I, and including second stack means spaced radially outward of the first stack means to provide an air passage therebetween, the upper end of the second stack means terminating a substantial distance above the upper end of the first stack means, and means for introducing air into the lower end of said passage whereby said air moves upwardly through said passage and is heated and merges with the gases at the upper end of the first stack means.

7. The structure of claim 6, wherein said second stack means is located on the outside of the casing and the lower end of the second stack means is spaced upwardly of the top wall of said casing.

8. A combustion device for burning combustible products in a gas, comprising a closed casing including a side wall, a top wall, and a bottom wall, an inner tubular member spaced inwardly of the outer wall of the casing to define an outer chamber therebetween and the interior of said tubular member defining an inner chamber, the lower end of said tubular member being sealed to said lower wall of the casing and the upper end of the tubular member being spaced from the upper wall of the casing to provide a passage that establishes communication between the outer and inner chambers, a first vertical stack located within the inner chamber and extending to the exterior of the casing, gas inlet means located at the lower end of the outer chamber and disposed generally tangentially of said outer chamber whereby gas containing com bustible products is introduced tangentially into said chamber and moves upwardly within the outer chamber in a generally spiral path, and through said passage and downwardly within the inner chamber in a spiral path to the stack, a burner unit located in the lower end of the outer chamber adjacent the gas inlet means, means for introducing fuel to said burner unit, means for supplying air under pressure to said burner unit, ignition means for igniting the fuel and air mixture in said burner unit, and a second stack spaced outwardly from the first stack to provide an annular air passage therebetween, said stack being located on the exterior of the casing and the upper end of the second stack terminating a substantial distance above the upper end of the first stack, air being drawn through the lower end of the passage and merging with the gas discharged from the upper end of the first stack to thereby provide complete combustion for the combustible products in said gas.

9. The apparatus of claim 8, wherein said passage comprises an upper chamber located at the upper end of the casing, said inner chamber having a larger volume than said upper chamber and said upper chamber having a larger volume than said outer chamber.

10. The apparatus of claim 8, and including second air supply means for supplying air under pressure to said outer chamber and located above said first named air supply means.

11. The apparatus of claim 8, and including third air supply means for supplying air to said passage.

12. The apparatus of claim 8, and including outlet means communicating with the lower end of said inner chamber, and adjustable means for introducing air through said outlet means to said inner chamber.

13. A combustion device for burning combustible products in a gas, comprising a closed casing including a side wall, a top wall, and a bottom wall, an inner tubular member spaced inwardly of the outer wall of the casing to define an outer chamber therebetween and the interior of said tubular member defining an inner chamber,- gas inlet means located at one end of said outer chamber and extending generally tangentially of said outer chamber for supplying a gas containing combustible product to the outer chamber, conduit means connecting the opposite end of said outer chamber with a first end of said inner chamber, said gas traveling in a swirling path through said outer chamber and through said conduit means to said inner chamber, burner means located adjacent said gas inlet means for burning said combustible products in the gas, stack means located within the inner chamber and extending to the exterior of the casing for discharging the gases from the inner chamber, said stack means including an inner stack communicating with the inner chamber and an outer stack disposed on the exterior of the casing and spaced radially outward of said inner stack to provide an air passage therebetween, the upper end of said outer stack terminating a substantial distance above the upper end of said inner stack, whereby air is drawn into the lower end of said air passage and travels upwardly through said passage and merges with the gases at the upper end of the inner stack to provide a secondary combustion zone.

14. The apparatus of claim 3, and including check valve means located between said blower means and the outer chamber for permitting flow of gas in a direction from the blower means to said outer chamber and for preventing flow of gas in the opposite direction. 

2. The apparatus of claim 1, wherein said casing and said tubular member are formed of refactory material.
 3. The apparatus of claim 1, wherein said burner means includes means for introducing fuel to said burner means, blower means for introducing air to said burner means, and ignition means for igniting the fuel and air mixture.
 4. The apparatus of claim 3, wherein said means for introducing fuel includes a conduit and valve means located in the conduit, said apparatus also including temperature responsive means responsive to the temperature within the casing and operably connected to said valve means to thereby control the flow of fuel to the burner means in accordance with temperature conditions in said casing.
 5. The apparatus of claim 4, wherein said valve means is provided with a high-flow position and a low-flow position and said temperature responsive means operates to move said valve means between said high-flow and low-flow positions.
 6. The apparatus of claim 1, and including second stack means spaced radially outward of the first stack means to provide an air passage therebetween, the upper end of the second stack means terminating a substantial distance above the upper end of the first stack means, and means for introduciNg air into the lower end of said passage whereby said air moves upwardly through said passage and is heated and merges with the gases at the upper end of the first stack means.
 7. The structure of claim 6, wherein said second stack means is located on the outside of the casing and the lower end of the second stack means is spaced upwardly of the top wall of said casing.
 8. A combustion device for burning combustible products in a gas, comprising a closed casing including a side wall, a top wall, and a bottom wall, an inner tubular member spaced inwardly of the outer wall of the casing to define an outer chamber therebetween and the interior of said tubular member defining an inner chamber, the lower end of said tubular member being sealed to said lower wall of the casing and the upper end of the tubular member being spaced from the upper wall of the casing to provide a passage that establishes communication between the outer and inner chambers, a first vertical stack located within the inner chamber and extending to the exterior of the casing, gas inlet means located at the lower end of the outer chamber and disposed generally tangentially of said outer chamber whereby gas containing combustible products is introduced tangentially into said chamber and moves upwardly within the outer chamber in a generally spiral path, and through said passage and downwardly within the inner chamber in a spiral path to the stack, a burner unit located in the lower end of the outer chamber adjacent the gas inlet means, means for introducing fuel to said burner unit, means for supplying air under pressure to said burner unit, ignition means for igniting the fuel and air mixture in said burner unit, and a second stack spaced outwardly from the first stack to provide an annular air passage therebetween, said stack being located on the exterior of the casing and the upper end of the second stack terminating a substantial distance above the upper end of the first stack, air being drawn through the lower end of the passage and merging with the gas discharged from the upper end of the first stack to thereby provide complete combustion for the combustible products in said gas.
 9. The apparatus of claim 8, wherein said passage comprises an upper chamber located at the upper end of the casing, said inner chamber having a larger volume than said upper chamber and said upper chamber having a larger volume than said outer chamber.
 10. The apparatus of claim 8, and including second air supply means for supplying air under pressure to said outer chamber and located above said first named air supply means.
 11. The apparatus of claim 8, and including third air supply means for supplying air to said passage.
 12. The apparatus of claim 8, and including outlet means communicating with the lower end of said inner chamber, and adjustable means for introducing air through said outlet means to said inner chamber.
 13. A combustion device for burning combustible products in a gas, comprising a closed casing including a side wall, a top wall, and a bottom wall, an inner tubular member spaced inwardly of the outer wall of the casing to define an outer chamber therebetween and the interior of said tubular member defining an inner chamber, gas inlet means located at one end of said outer chamber and extending generally tangentially of said outer chamber for supplying a gas containing combustible product to the outer chamber, conduit means connecting the opposite end of said outer chamber with a first end of said inner chamber, said gas traveling in a swirling path through said outer chamber and through said conduit means to said inner chamber, burner means located adjacent said gas inlet means for burning said combustible products in the gas, stack means located within the inner chamber and extending to the exterior of the casing for discharging the gases from the inner chamber, said stack means including an inner stack communicating with the inner chamber and an outer stack disposed on the exterior of the Casing and spaced radially outward of said inner stack to provide an air passage therebetween, the upper end of said outer stack terminating a substantial distance above the upper end of said inner stack, whereby air is drawn into the lower end of said air passage and travels upwardly through said passage and merges with the gases at the upper end of the inner stack to provide a secondary combustion zone.
 14. The apparatus of claim 3, and including check valve means located between said blower means and the outer chamber for permitting flow of gas in a direction from the blower means to said outer chamber and for preventing flow of gas in the opposite direction. 